2 Answers
2

You can enable this option (It's disabled by default) in the configuration manager. This should be available through Applications -> System Tools -> Configuration Manager (The System Tools menu may be hidden - you can make it visible by going to System -> Preferences -> Main Menu and selecting the checkbox next to System Tools, and possibly the one next to Configuration Editor in side the System Tools menu). Alternatively you can run gconf-tool from the command line.

You'll need to navigate to desktop -> gnome -> interface

Select menus_have_icons and check the box.

If you want the quick one liner you can enter the following in your terminal